A compound archery bow includes a bowstring operative in conjunction with one or two particularly configured cam assemblies (also referred to as pulleys), which serve to transfer energy between the resilient limbs of the bow and a bowstring so as to control the force/draw profile of the bow. In the operation of a typical compound bow, portions of the length of the bowstring are wound into and let out of various grooves in the cam assembly thereby varying the effective length of the bowstring and influencing the force/draw profile of the bow, which is understood to be the force which is required to displace the nock point of the bowstring over a particular distance. It is to be understood that in some instances, a compound bow will include a single, continuous bowstring which wraps around and extends between pulleys or cams associated with both of the bow limbs; while in other instances, a compound bow will include a bowstring comprised of several separate segments which may be variously affixed to different portions of the bow and cam assemblies. In all instances, such continuous or segmented strings are referred to herein as the bowstring or simply the string.
As will be explained in detail hereinbelow, the present invention is directed to a specific design of archery bow cam assembly which is referred to as a dual feed-out cam. In it, a primary string feed-out is operative to feed out a length of bowstring as the bow is drawn. A secondary string feed-out controls the feed out of another portion of the bowstring (either a continuous portion or a discrete portion as described above) during the time the primary portion of the bowstring is being drawn. In a two cam bow system, the fed out portion of string from the secondary feed is typically taken up by a take-up groove on a paired cam. The portion of the cam which takes up the string fed by the secondary feed-out is typically referred to as the “power cam” or power portion of the cam. When the cam assembly of the present invention is incorporated into a single cam bow system, the fed out string goes to an idler wheel and/or to the axle supporting the idler wheel on the opposite limb.
Some dual feed-out cam systems of the prior art are disclosed in U.S. Pat. Nos. 6,247,466 and 6,990,970, and the cam system of the present invention has advantages over such prior art cam systems, insofar as the secondary feed-out operates to initially shorten, and then lengthen, the portion of string being fed out as the bowstring is being drawn. This results in a faster build up of force in the force draw curve which results in more energy being stored. In addition, operation in this shortened/lengthened mode helps to maintain synchronization of cam assemblies in the case of a dual cam bow system. The cam system of the present invention also has advantages with regard to weight and cost over prior art cam systems such as that shown in U.S. Pat. No. 6,247,466 insofar as it avoids the need for expensive, bulky, and failure-prone bearing assemblies. These and other advantages of the invention will be apparent from the drawings, discussion and description which follow.